Inventions on the optical RF stereo, radar, and RF networks have laid the new foundations for the radar and electronic warfare technologies. The optical RF stereo utilizes optical fibers or direct lasers to achieve RF transmission and reception of widely separated RF antennas. The purposes are to setup smart RF deceptions for countering RF threats, to carry out live battle field deceptions, to assess the success of deceptions, to locate individual RF emitters hidden in RF environment for electronic intelligence gathering, as well as other applications. A recent Navy and Air Force program on the integrated defense electronic countermeasure (IDECM) is a sample of this invention.
The optical bistatic radar utilizes optical fibers or direct lasers to transit RF signals from the bistatic receiving sites directly to the transmitting site for processing. The functional objectives are to eliminate the problems associated with the conventional bistatic radars, to lower costs, and to increase the functional capabilities of radar networks. The purposes are for advancing the technology of bistatic radars, ensuring air traffic safety, managing highway traffic, monitoring ship movements in a harbor, gathering weather data, managing wild life, optimizing battle engagements, deterring low observables, and developing smart hard kill means.
The optical fiber based radars utilize optical fibers to store the initially transmitted RF signals for comparison with RF signals from reflection. Their functional objectives are to overcome or suppress the electromagnetic instabilities, to eliminate the locked waiting of RF synthesizers, to reduce the frequency of RF emissions, to dispose stringent inter pulse coherence requirements, to remove both range and Doppler ambiguities. Their purposes are for removing the system instabilities, reducing electromagnetic interferences, eliminating clutter contaminations, repelling hostile jamming and deception, suppressing the number of radar emitters, and halting the proliferation of radar systems.
The optical RF network utilizes optical fibers to centralize the RF signal generators and receivers. The network provides a new, generic, and versatile architecture for integrating the radar and electronic warfare systems. Its importance is analogous to the evolution of home entertainment systems. Forty years ago, home entertainment systems are packaged into consoles. As the technology evolves, in order to bring in the new advancements, the old system has to be discarded and replaced completely. The cost was too high for market penetration. To lower the costs of replacement and market barrier, the electronic industry abandoned the console architecture and divided individual systems into components. An upgrade is only limited to the outdated components, and not the entire system. The change drastically lowered the cost barrier in bring new technology to every home. The electronic entertainment market expands.
Component based systems have many other advantages as well in comparison with the console based systems. The speakers of a home entertainment system must be place in proper places within a listening room in order to create the realistic sound effects. It can be met by a component system, but not by a console system. Furthermore, most families have limited space in their listening rooms. It is impossible for them to accommodate the bulky consoles, but they always can make rooms for the smaller components. The evolution of home entertainment systems has led to the demise of console based systems.
The fielded radar and electronic warfare systems are all console based systems. They suffer the same deficiencies as the console based home entertainment systems, and are very costly. We just can not afford to upgrade them. Radar and electronic warfare systems in operation today are at least twenty years behind the latest technologies. Furthermore, these systems are too bulky and vulnerable. Their radar cross sections are large, and are obvious targets for missiles. One may ask, why did we not abandon the console and adopt the component based architectures for the radar and electronic warfare systems? There was a technical barrier. The architecture of component based home entertainment systems requires good audio and video connections. Coaxial cables are able to fill the requirement. However the architecture of component based radar and electronic warfare systems requires good RF connections. Coaxial cables as well as wave guides can not provide good RF connections. No other means existed. It was impossible to have the component based radar and electronic warfare systems until recently. Newly advanced optical fibers remove the technical barrier and lead to the invention of optical RF network. With the new architecture, the future radar and electronic warfare systems will not be outdated by the rapid evolution of the technologies.
Furthermore, optical RF network is an excellent vehicle in adopting the commercial off the shelf technologies. Radar and electronic warfare systems are functional specific, and are comprised of many common subsystems. However most of their subsystems are generic and readily available off the shelf. It was packaging that split these subsystem apart and forced them into consoles. The packaging excluded the use of commercial off the shelf technologies, and prevented the sharing of common subsystems. Without consoles, the restrictions imposed by packaging are eliminated.
The interferoceiver utilizes RF signal train generator to store transient RF signals and to regenerate their identical replicas for repeated analysis. Radar pulses are transient. It is a very important discovery on the investigations of transient phenomena and the radar signal processing. Since transient RF signals are so short, it was totally impossible to decipher all the information contained with a single transient RF signal. The present methods of processing transient RF signals are borrowed directly from that of processing communication signals.
Communication and transient signals are completely different. Communication signals are repetitive. We need a repetitive signal in order to have a pitch sensation. Except in very limited cases, transient signals vary from event to event and each transient signal is different. The super heterodyne technique invented by Edwin H. Armstrong is for processing the repetitive signals, not for the transient signals. Filtering and down conversion from RF to intermediate frequency (IF) are the essential steps in the method of super heterodyne signal processing. Although these steps have no diverse effects on the repetitive signals, but wipe out many essential features of a transient signal. The inability of the super heterodyne technique in handling a transient signal leads to the use of multiple transient signals, and demands these transient signals repetitively the same.
Most natural transient phenomena are not repetitive. Each radar pulse is distinct. It contains the range, Doppler, and intrinsic characteristics of a target. The inabilities of the present processing methods causes proliferation of radar systems, chaos of radar emissions, and hopelessness on passive target identifications. The interferoceiver, which was first revealed in the invention of optical fiber based radars, changes everything. The fundament problems associated with supper heterodyne techniques in radar signal processing will be eliminated.
Inventions on the optical RF stereo, serrated-roll edge for microwave antennas, and optimum edges for acoustical antennas have advanced similarities and commonalties of RF and acoustical systems or antennas to new levels. The serrated-roll edges reduce the side lobes of RF and acoustical antennas, and forge the directional antennas more directional. The objectives of these invented edges are to enhance the performances of RF and acoustical systems.
Our inventions have revolutionized the radar, and electronic warfare technologies. Efforts have started for the implementation and realization of the inventions. However, we are not satisfied with the success and continue to seek new ways in refining and advancing the inventions. We discovered some problems in our earlier inventions. One of them is the mechanical instabilities, which are more pronounced for the systems installed on movable platforms. Others are associated with the continuous probing RF waves and the weak transient signals in using interferoceivers.
The performances of optical RF stereo and radar systems depend on the knowledge of the state vectors describing separations or orientations of their respective antennas. The main objectives of these systems are for gathering information on the objects of interest. This requires that the systems be able to track or follow the said objects. Without a knowledge of the respective state vectors, these systems can not perform their tasks. As those of ordinary skill in the art can readily appreciate, the same kinds of problems are also presented in conventional RF, acoustical, sensor, and stereo systems. Likewise, the performances of nonrigid or profiled phase arrays, whether they are RF or acoustical, depends on the knowledge of the state vectors describing the locations or phase centers of their respective elements.
The tasks of tracking and following may not be difficult to accomplish for information gathering systems on fixed platforms. The tasks become more challenging on the movable platforms. When the movable platforms are in motion, they change their own state vectors in describing their headings, attitudes, vibrations, rotations, other internal motions and instabilities. Whether an object of interest is stationary or not, the aspect orientations and apparent locations of the object with respect to the moving platforms will be constantly changing, which in turn affects the performances of any sensors, cameras, or systems on the moving platform. The task becomes even more insurmountable in tracing and following the phase centers of the RF or acoustical antennas mounted on movable platforms.
Usual approaches to overcome the difficulty were to force the moving platforms in uniform motions and to suppress the internal vibrations and instabilities, for instance in synthetic aperture radar operations. The restrictions, which reduce the difficulties in tracking state vectors, exclude many interesting applications. As those of ordinary skill in the art should readily appreciate, one must advance the capabilities of tracking state vectors.
Similar situations are existed in monitoring the integrity of extended objects like buildings, bridges, and many other man made structures. As they slowly deteriorate with time, the state vectors in describing their vibrations, twistings, bendings, and other distortions undergo different changes, which in turn become are good indicators on their states of deterioration. As those of ordinary skill in the art can readily appreciate, it is also not a simple task to track these state vectors.
Similar situations exist in monitoring the actions of extended objects which may be linked together, for example the human body has body parts linked together by joints. Direct measurement of human motions and movements are often needed for generating graphic animation, virtual reality simulation, robotic control, teleoperation, medical diagnostic and rehabilitation purposes. Furthermore, in medical diagnosis and treatment such as magnetic resonance imaging (MRI) and stereotaxis, the position and motion of the body parts must be known precisely. As those of ordinary skill in the art should readily appreciate, it has been difficult to provide an excellent and precise method in measuring these motions and movements for many engineering and medical uses.
In light of the above, there is a need in the art for apparatus, which are universal and to track and trace the state vectors in describing radar, sonar, stereo, and other information gathering systems; fixed and moving platforms; as well as extended objects. Furthermore, they should be abe to handle the dynamical situations.